There are those who believe the bombs and blood were staged, the amputees and others injured were actors in some kind of Hollywood production designed to justify martial law.

Others acknowledge the carnage but say it was perpetrated by a secret squad of special operations soldiers. And there are those who insist that inconsistencies in early reports, erroneous statements by public officials, and unreleased evidence from prosecutors — among other things — reflect anything from a government coverup to an effort to frame the suspects.

Three months after two bombs detonated near the finish line of the Boston Marathon, killing three and injuring more than 260, skeptics and conspiracy theorists from around the world have coalesced on Facebook, Twitter, and elsewhere — including at an acrimonious appearance this month in federal court in Boston — to defend Dzhokhar Tsarnaev.

They are making their case despite a trove of evidence that the surviving suspect and his older brother Tamerlan planted the bombs, including footage of them at the scene carrying bulky backpacks; Tamerlan's death in a shootout after allegedly lobbing bombs at police in Watertown; and the discovery of Dzhokhar hiding a few blocks away in a shrink-wrapped boat, where he allegedly scrawled a confession.

While accused villains have long attracted adamant defenders and conspiracy theorists, the global range and voluble intensity of the so-called Free Jahar movement has sparked dismay and denunciations on behalf of those who lost their limbs or lives in the bombings.

"Their claims are an affront to the victims, the country, and overall decency,” said Nancy Savage, executive director of the Virginia-based Society of Former Agents of the FBI, who served for years as a supervisor on terrorism cases. “They're grasping at little pieces here and there that we can't know about until the evidence is tested and presented in court. Millions of dollars are going to be spent by taxpayers to make sure he gets a proper defense.”

One invitation-only Facebook group called Dzhokhar Tsarnaev is Innocent has more than 13,500 members from Australia, Brazil, China, Russia, the United States, and beyond. They started a defense fund on the alleged terrorist's 20th birthday this week, and members have launched websites responding to the sweeping, 30-count federal indictment, which accuses Tsarnaev of using weapons of mass destruction to slaughter spectators on Boylston Street, killing a Massachusetts Institute of Technology police officer, and firing at officers pursuing the brothers in Watertown.

On YouTube, Tsarnaev supporters have posted hundreds of videos, some of which have attracted hundreds of thousands of views. There are those like “Dzhokhar Tsarvaev (Jahar) is Cute,” which has been viewed nearly 100,000 times and features a young woman who compares Tsarnaev to the Jonas Brothers. Other popular videos portray the Cambridge Rindge and Latin School graduate as “normal as you are,” and feature a montage of images of him dancing, wrestling, and going to the prom. There are those set to ominous music that raise questions about everything from whether Tsarnaev could have carried a pressure cooker bomb on one shoulder, as surveillance photos show, to those using graphics to raise questions about the authenticity of victims' wounds.

On Twitter, more than 85,000 people are following Tsarnaev, and scores, if not more, of supporters are using his photo for their profile picture. One group called “We are the Lion,” which urges its members to tweet under the #Justice4Jahar hashtag, features a poll on its website that shows nearly 90 percent of its members are women, nearly two-thirds are age 25 or younger, and one-third live outside the United States.

Among those convinced Tsarnaev is innocent is Rebecca Lynn Crovello, 20, a pregnant mother from Somerville who studies psychology at Bunker Hill Community College.

“The pieces of the puzzle just don't match up,” she said of the 74-page indictment released last month in federal court. “I think it was a setup. I know for a fact that he's innocent.”

She has looked at the proliferating websites and other groups online, and has seen pictures from the Marathon route of uniformed men wearing military-style patches. That has led her and others to say the bombing was the work of a secret team of Navy SEALs. “I don't know why they would do it, but it was probably because they get their orders from the government,” she said.

When asked whether there was something about Tsarnaev that has led her to join a Facebook group calling for him to be freed, she said: “I can sort of relate to him. He's a handsome kid, and obviously there are going to be girls attracted to him because he's good-looking. But that's not why I'm interested in his innocence.”

Others also say it's unfair to pigeonhole his supporters as hybristophiles, the term for those who are sexually attracted to people who have committed gruesome crimes.

“There are a lot of young girls who were going on his looks,” said Neda Kadri, 31, who works in public relations in Detroit and is a member of one Facebook group supporting Tsarnaev. “But for us, there are the things that don't add up. We absolutely believe in his innocence.”

In explaining their views, those backing Tsarnaev say that the images of the backpacks presented by police shortly after the bombings do not match the backpacks shown in surveillance photos, even though they were ripped apart during the explosions. They say they can't believe the charges until authorities reveal images of the brothers setting down their bags exactly where the explosions occurred.

Others say they can't believe Dzhokhar Tsarnaev could have committed the crimes because he wasn't overtly religious, even though prosecutors say he downloaded extremist Islamic propaganda from the Internet, and police say he and his brother brought five bombs, a semiautomatic handgun, a machete, and a hunting knife to the battle with police in Watertown.

Jeanne M. Kempthorne, a former federal prosecutor who now works at a criminal defense lawyer in Salem, said she isn't surprised to see contrarians in such a big case.

“It's just human nature,” she said. “There will always be flat-earthers or grassy knoll types, people who will go to great lengths to dispute the obvious or find conspiracies or come up with evidence-free speculation.”

But Tsarnaev supporters insist that they are the skeptical ones, that anyone who buys the government's case is being willfully blind.

Lindy Urso, 45, a criminal defense lawyer in Stamford, Conn., said he “smelled something rotten” from the beginning of the investigation, and called the case since “a sham.”

As evidence of Tsarnaev's innocence, he cites an alleged link between the brothers and the CIA, the FBI's previous investigation of Tamerlan's visit to Russia last year, and what he considers a spate of implausible events on the night of the shoot-out in Watertown.

“I could easily just be a paranoid nut,” he said. “I don't think I am, but I hope I am. I hope I'm wrong.”

For all the doubters of Tsarnaev's guilt, Larry Marchese, a spokesman for the Richard family, whose 8-year-old son Martin died and whose 7-year-old daughter, Jane, lost a leg, said there can be no doubt that the attacks were “not only devastating but undeniable.”

The bomb allegedly planted beside them by Dzhokhar Tsarnaev also left the children's mother, Denise, with a head injury and damage to her vision. Their father, Bill, sustained shrapnel wounds, leg burns, and hearing loss. The oldest child, Henry, was unharmed.

"The bomb deliberately placed at the feet of the Richard family was very real,” he said. “Their pain is incredible and what they've been through has been relentless.”

It will be up to a jury to decide whether the case against Tsarnaev is fair, he said.

“But I don't understand how anyone can look at the collective evidence, ranging from the video surveillance to the manifesto he scrawled on the wall of a boat, and not think our legal system is marching in the right direction,” he said. “There is no doubt that what happened to the people on Boylston Street on April 15 was absolutely real, and to think otherwise is a perspective I cannot understand.”